Powder ejector assembly



June 6, 1961 c. B. MILTON POWDER EJECTOR ASSEMBLY Filed Aug. 29, 1957uwz/vror? CHARLES B. MLTON arfi/l/M A TTORNEV United States Patent2,987,221 POWDER EJECTOR ASSEMBLY Charles B. Milton, Matawan, NJ.,assignor to Union Carbide Corporation, a corporation of New York FiledAug. 29, 1957, Ser. No. 681,040 8 Claims. (Cl. 222-1) This inventionrelates to a powder dispensing device. More particularly it relates to anovel orifice-type powder ejector having improved flow characteristics.

Many industrial processes require the entrainment of a powder in a gasstream. The entraining gas may be either used as a simple carrier totransport a powder from one place to another where it is deposited andused in bulk form or it may be a critical agent in a process, as wherethe powder is entrained in the gas stream and then introduced into a potof molten metal wherein the stream velocity carries the powder well intothe melt and also greatly enhances mixing. Another widespread industrialuse of gas entrained powders in recent years has been in the field ofpowder-flame cutting, lancing and scarfing operations. There are, ofcourse, many other uses where the entraining of a finely divided orcoarse material on a gas stream is necessary.

In all of the above mentioned processes a number of basic requirementsmust be met by the dispensing equipment to obtain satisfactory results.Plugging of the valves and tubes in such equipment is often a seriousproblem especially where the powders are extremely fine or where thepowder is under pressure in the dispensing hopper. Such plugging mayresult in either complete failure of the equipment or in intermittentand erratic flow characteristics.

Where the powder is to be used in lancing operations it is oftennecessary to use pressures as high as 100 pounds per square inch in thetop of the hopper to obtain suitable powder flow with the lancingoperation. As stated previously, these pressures cause compacting andplugging in the ejector assembly. Further problems arise due to the backpressures created by long lengths of hose and the powder nozzles. Thisback pressure is also more acute in the 90 to 100 pounds per square inchrange required for powder lancing.

In the ejectors of the prior art there were a number of undesirablefeatures which resulted in frequent plugging of the apparatus and alsoin very uneven powder flow characteristics. All of these ejectorsutilize complex powder flow paths requiring the powder to make a numberof turns before entering the conveying air stream. Also, the smallpowder entry holes, often utilized, through which the powder had to flowvery often became clogged. This required shut-down of the equipment andcleaning said holes.

The majority of the prior art devices utilized an entraining gas streamof large cross-sectional area which made it very diflicult to obtainuniform powder distribution across the entire gas stream. Also, thepowder was introduced into the gas stream by pressure on the powder inthe dispenser rather than by a positive pickup by the gas stream per se.Nor is provision made in any of these devices for a secondary air supplyto facilitate unusually heavy powder flows as are required in somelancing operations.

It is accordingly an object of the present invention to provide a novelpowder ejector for use in available dispensing equipment which iscapable of producing a smooth and evenly metered powder flow.

It is a further object to produce such a metered flow in a high pressuresystem.

Another object is to provide an ejector which has a readily adjustablemetering rate.

2,987,221 Patented June 6, 1961 Other objects and advantages will beapparent from the accompanying specification and claims in which:

FIGURE 1 is a general View of an exemplary powder dispensing system,

FIGURE 2 is a view of a longitudinal section of the novel powder ejectorof the invention, and

FIGURE 3 is a perspective exploded View partly in section of the ejectorshowing the structural relationships of the parts.

According to this invention there is provided in a powder dispensingapparatus including a powder hopper, an improved ejector in the bottomthereof and convey ing hoses connected to the outlet means of saidejector, the ejector having means for metering a continuous flow ofpowder downwardly onto a substantially conical pile on a horizontallydisposed plate, means for providing a substantially annular gas streamwhich continuously entrains powder from the lower peripheral edge ofsaid conical pile, and apertures in the horizontally disposed plate forpermitting the annular gas stream containing the powder to pass downthrough the plate member without otherwise disturbing the continuouslysupplied pile of powder thereon and means located below the horizontallydisposed plate for directing the entrained powder stream into saidconveying means.

Referring to FIGURE 1 there is shown an exemplary powder dispensingsystem including a covered hopper 10, a first conduit 12 entering gastightly through the side thereof for maintaining pressure within thehopper and conduit means 14 which connects to the powder ejector withinthe hopper and supplies a conveying gas under appropriate pressure.Numeral 16 denotes generally the ejector assembly which, as may be seen,is located in the bottom of the hopper with suitable connection toconveying hoses 18 which in turn are connected to suitable cutting,lancing or scarfing torches and the like. It is to be understood thatthis over-all system is merely exemplary of a dispensing device as usedwith powderfiame operations and is not intended to limit the scope ofthe invention. Referring to FIGURES 2 and 3, the ejector assemblycomprises a main body member 20 having an axial passageway 22 with aconical upper area which connects directly with the powder space in thehopper and serves as the flow path for conducting the powder to ametering shelf 24. There is also provided a second passageway 26 throughthe main body which is laterally disposed from the axial passageway andconnects with a fitting 28 which is internally connected to a source ofconveying gas. At the end of the main body member there is provided ametering nozzle 30 having an axial bore therethrough aligned with thatof the main body member. This lower metering nozzle has an outsidediameter substantially less than the outer diameter of the main bodymember 20'. This metering nozzle may be either insertable in the mainbody member as shown or constructed as one piece with said body member.

A circular conduit member or annular gas distributor 32 is connectedwith the secondary passageway 26 through the main body member andcompletely encircles the lower portion or metering nozzle 30 of the mainbody portion. As may be seen, the outside diameter of this annular gasdistributor is also less than the outer di ameter of the main bodymember. Gas distributor 32 is provided with a plurality of downwardlydirected openings 34 through which the conveying gas is ejected. Itshould be stated that any means for obtaining an annular gas stream maybe provided such as an annular distribution chamber having a continuousannular opening in the bottom thereof.

A second body member 36 is attached to the main body member by suchmeans as threads 38 and is provided I l 3 with suitable slideablesealing means such as the O-ring 40. As may be seen from the drawing,the inner diameter of the second body member corresponds approximatelyto the outer diameter of the upper portion of the main body member 20this leaving an annular cavity 42 between the inner surface of thesecond body member and the outer surface of the metering nozzle 30. Thegas distributor 32 is thus located in the upper portion of this annularcavity and above the lower end of the metering nozzle 30.

The lower end of the cylindrical passage in the second body member isclosed by a horizontal metering plate or shelf 24. This shelf is soconstructed that a portion in the center thereof under the opening inthe metering nozzle 30 is continuous while openings 44 are providedaround the periphery of the continuous portion. The diameter of thecontinuous surface in the center of the horizontal metering shelf isdetermined by the angle of incline or repose of the powder beingentrained so that the powder resting on the shelf as fed by the meteringnozzle 30 will not fall through the openings when there is no gas flowand the hopper pressure is shut ofi. This diameter is of course, limitedby the maximum operable distance between the metering nozzle 30 andshelf 24. The openings 44 in the metering shelf are shown as arcnate inform; however, they may be of other shapes providing the continuous areaof the shelf is left undisturbed and that sufficient totalcross-sectional area of the openings themselves is provided.

A third body member 46 is provided which is securely fastened to thelower end of the second body member 36 which serves to direct powderflow into the suitable conveying means 18. There is also provided inthis third body member a tube 48 which is connected to the secondaryconveying gas source 50 and which is disposed with its irmer enddownwardly directed to direct the secondary gas flow along the axis ofthe bore of said third body member.

FIGURE 3 shows the relative positions of the various elements inperspective from which the adjustability of the main body 20 and thesecond body member 36 may be seen. The distance (A) between the edge ofthe metering nozzle and the metering shelf 24 may thus be readilyadjusted to obtain varying powder flows.

In operation, powder flows through the axial passageway 22 in the mainbody member 20 and metering nozzle 30 both under gravity and whatevergas pressure, if any, may be present in the hopper. The powder fallsupon the metering shelf 24 and forms an essentially conical pile betweenthe metering shelf and the lower end of the metering nozzle. The mainconveying gas stream passes through the openings 34 in the annular gasdistributor 32 which surrounds the metering nozzle 30 above the lowerend thereof and forms a substantially tubular or annular stream whichpasses down over the edges of the conical pile of powder and through theopenings 44 in the metering shelf 24. This annular gas stream entrainspowder from the exposed lower edges of the conical pile and due to therelatively thin wall section of the gas stream and to the continuouscontact said stream makes with the pile of powder around the entireperiphery thereof an extremely uniform amount of powder is entrained inthe gas stream for any given velocity of conveying gas. The gasentrained powder is directed into the suitable conduit means 18 by meansof the funnel shaped upper part of the third body member 46 locatedbelow the metering shelf 24.

When it is desired to change the powder flow rate either the hopperpressure may be altered and/or the distance (A) between the lower end ofthe metering nozzle 39 and the metering shelf 24 may be varied.Increasing either of these parameters will increase powder flow.

It has been found that when unusually heavy powder flows are required,the annular gas stream as limited by the discharge openings, by itself,is often insufiicient to carry the powder stream for substantialdistances although it will initially entrain almost any desired amountof powder in the stream; therefore, a secondary conveying gas inlet 48has been provided and placed in operation. This secondary conveying gassource is necessary only during such severe powder iiow requirements asfor lancing, and since it is introduced below the metering andentraining area it in no way affects the entrainment mechanism. Itincreases the gas flow, and thus the velocity in the conveying means 18and prevents any tendency of the powder to settle out and clog saidmeans.

The instant ejector has proved far superior to any tried for thespecific applications to which it has been put. The improved operatingcharacteristics are attributed to the following features:

(1) Stream-lined flow path. The powder flow path through the ejectorfrom the dispenser hopper to the conveying member is straight andunrestricted except for the powder metering orifice. This is the oneplace that the flow must be restricted in order to control quantity.

(2) The sharpened edge of the powder metering member 30. The area ofrestriction through which the powder must flow is thus held to a Thisreduces the tendency to plug when larger than usual powder particles areencountered.

(3) Replaceable powder metering member 30. The said member screws intothe main body of the ejector and may be easily replaced when worn. Also,different metering members are available for the different ranges ofoperation.

(4) The conveying gas stream issues from a circular member 32 havingopenings 34 contained therein thus completely contacting the powder tobe conveyed. Because of the design and positioning of the powdermetering nozzle 30 and shelf 24 a conical pile of powder is formed on around shelf. The conveying gas which encircles the orifice blowsdirectly down onto the powder cone. As a result, the powder is blown orsheared off the shelf and is picked up by the gas in a smooth andcontinuous manner. As this occurs, the dispenser hopper pressure assistsin moving the hopper powder down through the axial passageway 22 andmaintains the powder cone on the metering shelf. Thus, a tendency forerratic or pulsating powder pickup from the pile is eliminated since thepile is maintained at a uniform size and the conveying gas continues toflow at a constant velocity.

(5) The secondary conveying gas supply. The external fitting 48downstream from the metering orifice permits adding more conveying gasto the gas-powder-stream which thereby prov-ides the increased gasvelocity necessary for the conveyance of unusually large powder flows.

In summary, the powder rate may be determined by either the hopperpressure or the distance A between the lower end of the metering member33 and the metering shelf 24 while the gas-powder stream velocity isdependent primarily on the pressure of the main conveying gas source andif used, the pressure supplied at the secondary conveying gas inletmeans 48. In the instant example the system gas pressures must either beequal or provided from the same gas source to prevent arculatory flowwithin the system when the downstream end of the conveying means is shutoff.

It can thus be seen that there is provided a novel and useful powderejector for use in powder dispensing systems which gives resultsheretofore unobtainable.

The above description and drawings are to be taken as merely exemplary,the only limitations intended are those set forth in the followingclaims.

What is claimed is:

1. An orifice type powder ejector comprising a body having a passagetherethrough with a horizontally dis posed plate therein, means forproviding a continuous flow of powder on said horizontally disposedplate so as to form a substantially conical pile whose vertex extendsopposite to the direction of powder flow, means for providing asubstantially annular gas stream which continuously entrains powder fromthe lower peripheral surface of said conical pile, aperture means in thehorizontally disposed plate for permitting the annular gas streamcontaining the entrained powder to pass down through the plate memberwithout otherwise disturbing the continuously supplied, conical pile ofpowder thereon, and means located below the horizontally disposed platefor directing the entrained powder stream into suitable conduit means.

2. A powder ejector as set forth in claim 1 wherein said means locatedbelow the horizontally disposed plate includes an additional means forintroducing further gas into the gas entrained powder flow.

3. An orifice type powder ejector comprising a first body member withupper and lower portions having an axial passageway and a secondarypassageway therethrough, said secondary passageway being laterallydisplaced from said axial passageway, the lower portion of said firstbody having a reduced diameter so that the lower opening of thesecondary passageway extends without said lower portion and is displacedboth laterally and vertically from the lower opening of the axialpassageway, an annular gas distributor connecting with the lower end ofthe secondary passageway and disposed in a plane perpendicular to theaxis of and above the lower end of the first body whereby it encirclessaid first body, said annular gas distributor having a plurality ofdownwardly disposed discharge openings therein, a second body memberengaging the first body member and having an axial passagewaytherethrough having a diameter larger than the outer diameter of thelower portion of the first body member whereby an annular chamber isformed which contains said annular gas distributor member, ahorizontally disposed shelf in the lower end of said second body member,said shelf having a continuous surface whose diameter is greater thanthe diameter of said axial passageway of said first body member spacedfrom and centered below said lower end of said first body member andsaid shelf having at least one opening located about the periphery ofsaid continuous surface, and a third body member attached to the bottomof the second body member below the horizontally disposed shelf adaptedto direct material flowing through the ejector into a subsequent conduitmeans.

4. A powder ejector as set forth in claim 3 wherein the second bodymember is in axially movable engage ment with said first body memberwhereby the spacing between the lower end of the first body member andthe horizontally disposed shelf may be varied.

5. In a process for forming a gas borne powder stream, the stepscomprising providing a supply body of powder; causing a continuous flowof said powder from said body onto an essentially horizontal support soas to form a substantially conical pile whose vertex extends in theopposite direction of powder flow; providing an annular gas stream toflow in continuous contact with the lower peripheral edge of saidconical pile so as to entrain the powder therein and thereby forming thegas and entrained powder into a gas borne powder stream.

6. A process as set forth in claim 5 wherein the continuous powder flowfrom said body onto said horizontal support is regulated by pressurizingsaid body of powder.

7. A process as set forth in claim 5 wherein the rate of powderentrainment is regulated by adjusting the diameter of the base of saidconical pile.

8. A powder ejector as set forth in claim 1 in which said means forproviding a continuous flow of powder onto a substantially conical pilewhose vertex extends opposite to the direction of powder flow comprisesmeans defining a substantially vertical passage with a lower end spacedabove said horizontally disposed plate and means for adjusting thespacing of said lower end above the horizontal plate for regulating thepowder entrainment rate.

References Cited in the file of this patent UNITED STATES PATENTS2,011,133 Yoss Aug. 13, 1935 2,120,003 Schanz June 7, 1938 2,577,550Wahlin Dec. 4, 1951 2,594,476 Miller Apr. 29, 1952 FOREIGN PATENTS549,435 France Nov. 20, 1922

